1. Technical Field
The present invention relates to a printed circuit board and a method of manufacturing the printed circuit board.
2. Description of the Related Art
With advances in the electronics industry, there is a growing demand for electronic components that provide higher performance, more functionality, and smaller sizes, and naturally, there have appeared boards for high-density surface-mounted components, such as in an SiP (system in package) or 3D package, etc. To respond to the demands for boards of higher densities and lower thicknesses, there is a need for high-density connections between circuit pattern layers.
Methods of electrically interconnecting layers in a multilayer printed circuit board include methods of plating, methods of printing metal paste to fill via holes with a conductive material, and the so-called “B2IT” methods of implementing interlayer connection by means of conical paste bumps.
The requirements in current printed circuit boards are closely related to the trends of faster performance and higher densities in the electronics market, and to satisfy such requirements, the printed circuit board faces several tasks, such as providing finer circuits, superior electrical properties, higher reliability, higher signal transfer speeds, and greater functionality, etc.
Current electronic products are rapidly progressing towards even greater functionality and even higher speeds. To keep abreast of these trends, the semiconductor chip is undergoing even more rapid developments, as is the board for connecting the semiconductor chip to the main board.
FIG. 1 through FIG. 6 are cross-sectional views representing a flow diagram of a method of manufacturing a printed circuit board according to the related art. Referring to FIGS. 1 to 6, through-holes are processed in a copper clad laminate, which has copper layers formed on either sides of an insulation layer 102, after which electroplating is performed to form vias 106, and an insulating resin 103 is filled inside the inner walls of the vias 106. When the vias 106 are formed for electrically connecting the layers, circuit patterns 104 are formed on the surfaces of the insulation layers to fabricate an inner substrate.
A build-up layer 108 of an insulating material is stacked on each side of the inner substrate, and blind via holes 109 are filled by way of plating to form blind vias 110. Then, circuit patterns 112 are formed on the outermost layers to build up the board. Such build-up layers are stacked on the inner substrate in multiple layers, and solder resists 114 for protecting the circuits are coated on the outermost build-up layers 108 to fabricate a multilayer printed circuit board of a high density.
However, while high-density interlayer connection is required to meet the demands for boards with higher densities and lower thicknesses, there is a limit to implementing high-density interlayer connections when forming vias according to the related art.
Also, methods of manufacturing a printed circuit board according to the related art can lead to the scale of the board being altered, due to the high coefficients of thermal expansion of the insulation layers and the heat generated during the manufacturing process, and can lead to incorrect registration between layers, causing problems in the transfer of electrical signals.
Also, as the coefficient of thermal expansion may be much greater for the solder resists than for the insulation layers, there is a risk of cracks occurring.
Furthermore, while high evenness is required for implementing high densities in a printed circuit board, and such evenness of a board surface is determined by the solder resist, there is a limit to increasing the evenness of the board surface when applying a liquid type solder resist according to the related art.